The present invention relates to braking systems for passenger conveyors. More particularly, the present invention relates to main drive shaft brakes used to halt passenger conveyors in the event of an emergency or otherwise abnormal condition.
Conventional passenger conveyors, such as moving walkways or escalators, include a series of pallets or steps that move in a closed loop. Passenger conveyors allow people to stand or walk along the steps while being transported across a distance. The steps are typically attached to a step chain, which provides forward movement to the steps. More specifically, a drive sheave imparts motion to step chains thereby moving the steps, and any people located on the steps, along a predetermined track. For escalators, the track extends between a lower elevation and a higher elevation and back to the lower elevation in a closed loop. Moving walkways can have inclined, declined, or substantially flat tracks and sometimes include a pair of oppositely traveling, parallel walkways.
For some reasons passenger conveyors include both a machine brake and a main drive shaft brake. The machine brake is activated to prevent further movement of the step chain under normal conditions. For example, if the passenger conveyor is shut down for the evening or if repairs are needed, the machine brake will stop the step chain and hold the passenger steps in a stationary condition. The main drive shaft brake, or “auxiliary brake” as it is sometimes referred to, is an additional braking system that can be activated to halt movement of the step chain to avoid damage to the passenger conveyor and/or prevent passenger injury.